Gaseous-fuel burner



Oct. 30, 1928.

C. F. HAMMOND GASEOUS FUEL BURNER Filed June 3, 1926 2 Sheets-Sheet 1Oct. 30, 1928.

C. F. HAMMOND GASEOUS FUEL BURNER 2 Sheets-Sheet Filed June 2, 1926 gsiPatented Oct. 30, 1928.

UNITED STATES PATE-NT OFFICE.

CECIL FEATHEBBTONE HAMMOND, OF'LONDON, ENGLAND, ASSIGNOB OF ONE-FIFTH T0WILLIAM SHACKLETON, 0F LONDON, ENGLAND,

GAsnoUs-IUEL summa.

Application med .Tune 2, 1926, Serial No. 113,191, and in Great Britain.Tune 2, 1925.

This invention relates to improvements in and connected with burners forthe combustion of liquid, gaseous or powdered fuel and is applicable foruse in steam generation, chemical concentration and other heatingoperations. The improvements are particularly concerned with burnersadapted for being immersed in the liquid or body to be heated. It isvery desirable that such burners should have a capacity for producingintenseheat and attaining a complete combustion of the fuel within theburner. In the event of combustion Within the burner being incomplete,combustible particles escape with the gases of combustion into theliquid to be heated and are instantly cooled by such liquid so that theyare Wasted and not consumed. It has been realized that it is necessaryto provide for the intimate mixing of the air and fuel before reachingthe combustion chamber and to avoid overheating of the mixture.Consequently mixing tubes have been employed and these tubes were cooledor notexposed to the high temperature which the combustion chamber mustwithstand. Also, to prevent overheating or fusing of the materials ofwhich the combustion chamber is made, air jacket cooling has beenresorted to.

The object of the present invention is to provide a construction ofsubmersible burner possessing the desirable characteristics abovereferred to, and capable of producing and maintaining for long periodscomplete combustion within itself without liability of firing back. Afurther object is to provide an assemblage of burner parts such as willensure a maximum degree of safety for those parts and enable acombustion chamber part, for example, to be exchanged or renewed withoutdifficulty or much loss of time.

Accordz'ng to this invention, the burner comprises two tubular parts ofdifferent diameter and freely communicating one wit-h the other, thepart of smaller bore being the mixing chamber which is adapted ordesigned so that it is maintained at a lower temperature and .the partof larger bore being the combustion chamber which is `adapted ordesigned so that it accumulates heat and is thereby maintained at a hightemperature, the length of the mixing Chamber being pre-determined forensuring proper mixing and the length of the combust-ion chamber beingpredetermined for ensuring complete combustion within the burner. Thefuel and air admission means are suitably deslgned for promoting mixtureof the fuel and air and imparting a considerable` velocity of flowthrough the mixing chamber.

Ihe reliability of such a burner in o eration is explained by the factthat the ve ocity of the mixture through the mixing tube exceeds thevelocity of propagation of flame, so that once the burner has beenignited and started, the flame is carried forward into the combustionchamber and cannot strike back so long as the normal admissionconditions of the fuel and air are preserved. In order that theaforesaid velocity may be maintained, there must be free communicationbetween the mixing tube and combustion chamber, and in order that thecombustion may be complete before the burner nozzle is reached, thetubular combustion chamber must have a proper' length, capacity andtemperature as will be readily understood.

In the operation of this burner, a temperature of 850o C. and over, ismaintained at the inner surface of the combustion chamber, and a.surfaceheated to this degree exercises a catalytic action on the constituentsof the combustible mixture coming into contact with it, this actionbeing conducive to the complete combustion which takes place entirelywithin the combustion chamber as aforesaid. At the same time, the partsare designed, or expedients are adopted, to prevent overheating andfusing of the walls or parts of the combustion chamber.

The burner nozzle is advantageously contracted or of so-called venacontracta form so that the incandescent gases making their exit acquirevelocity and penetrate the liquid to be heated. Moreover, this form ofnozzle is of particular utility, for example, when the burne-r isemployed for the concentration of salt solutions as it eliminates lowpressure zones within the combustion chamber and resists creeping of thesalt into the chamber which consequently is not liable to become fouledby salt deposit.

The combustion chamber is of such a nature as to acquire and preserve,during the operation of the burner, a radiant temperature calculated topromote the desired combustion. AThus, Aan intensely hot flame isproduced, the combustion is completed within the chamber, and the gasesof combustion are ejected from the nozzle with no Y reducing tendency toeddy back or return and dilute the combustible mixture in process ofcombustion.

The combustion chamber is advan tageousl of refractory material, or .hasa 11ning o refractory material, and 1s adapted for holding anappropriate quantity of heat. So long as this condition is observed, thewalls of the combustion chamber may be solid or hollow and may belagged, or provided with heat insulation, and such insulation may be avacuous space, a dead air s ace, or the equivalent. The combust1on camber may be enclosed in an outer casing of meta, glass, or othersuitable material.

As refractory and other parts of the burner cannot safely be connectedtogether by ordinary bolt and nut or like r1g1d mechanical connections,and as ex ansion,

and contraction must be provided or, the

parts constituting the assemblage are held together by elastic orresilient means. Moreover, the joints are made tight, and danger offracture is reduced by the insertion of packing rings between the parts.

By suitable arrangement of the air and fuel admissions, it is possibleto avoid obstruction in the whole length of the tubular burner and toprovide an observation window in the end cover for enabling the operatorto observe the flame and exercise intelligently an appropriate controlof the combustion.

And in order that the invention may be easily understood and readilycarried into effect, reference will be made to the accompanyingdrawings, illustrating several submersible burners constructed accordingto this invention in whichdrawingsw- Figure l is a longitudinal section,and

Figure 2 is an elevation of a simple construction of burner.

Figure 3 is a longitudinal section of a modification. v

Figure 4 is a section on the line IV-IV of Figure 3, and

Figure 5 is a section on the line V-V of Figure 3.

Figures 6, 7 and 8 are longitudinal sections of parts of furthermodification, and

Figure 9 is a sectional plan of a fragment of Fi ure 8.

In igures 1 and 2, the burner comprises an elongated cylindrical metalcasing a, internally flanged at b at the forward end to retain arefractory burner nozzle c of vena contracta shape. The casing a isprovided with an external fiange d at the rear end for the mounting of aseries of screw studs e. Into the rear end of the casing is passed abushing or sleeve f of metal or other suitable material, said bushinghaving a flange g perforated to freel pass over the studs e, in order toallow or contraction and expansion. The studs e serve for the mountingof a perforated an e 7L of an air .and gas supply itting z'. Hellcal srings lo are passed on to the studs e, an nuts Z engaging washersbearing upon the said springs cause the latter to bear on the flange handdraw the parts tightly together. At the forward end of the reducingbushing f there is a refractory nipple or nozzle m formed at its forwardend with a spigot portion m the bore of which is flared at the forwardend. A hollow cylinder fn. of refractory material constitutes thecombus-` l tion chamber and has an internal diameter corresponding tothe external diameter of the spigot m of the refractory nipple m. Thiscylinder ln, is inserted in the casing between the vena contracta nozzlec and the nipple m, with the spigot of the latter entering the bore ofthe combustionchamber fn. A ringo of asbestos or the like is interposedbetween the fiange b and the nozzle c and a packing ring p may beinterposed between lthe nipple m and the combustion chamber n.

The combustion chamber fn, has an external diameter somewhat less thanthe internal diameter of the casing a to allow of being encircled withasbestos cord w or other insulating material; Or, the annular spacebetween the metal casing a and the combustion chamber n may be a deadair space. The air and gas supply fitting i is of substantiallycylindrical form and comprises two concentric chambers g and o, theouter chamber q having a lateral connection s (Fig. 2) for the supply ofair under pressure and communicating with the central cham\ ber 1-through a series of ports t. The central chamber 1" encloses acontracting nozzle u directed towards the bore of the reducing bushingor mixing chamber f and adapted at the rear end for connection by ascrew coupling v with a gas supply pipe. Also, the exit from the chamber'l' is of coned orl nozzle formation. Gas from the nozzle u mixes withair admitted through the ports t, and the stream of mixture isv directedinto the bore of the bushing f. Iyhe latter provides a passage ofreduced cross sectional area between the air and gas'supply fitting andthe combustion chamber n and the length thereof is sufcient for enablingan intimate mixture of air and gas to be effected by the time that thecombustion chamber is reached. In this example the mixing chamber f isof a length equal to about two thirds of the length o the burner casinga;

The streams of air and fuel being injected into the bore of the bushingf at hlgh Velocity b the nozzle combination become thoroughly mixed intheir passage. Upon being ignited by suitable means, combustion takesplace in the chamber n, so that the refractory wall becomes heated to ahigh temperature. The' mixture emerging from the nipple m a partition10, a nozzle 11, which constitutes expands instantly in the chamber 'n-and loses velocity and comes into contact with theheated wall andcomplete combustion of the mixture is effected within the chamber n sothat no unconsumed fuel remains at the moment that t-he gases ofcombustion make their exit at increased velocity throu h the nozzle c.The bushing f being prefera ly `f metal or alloy, does not becomeoverheated owing to its conductivity and the cooling'at its exterior. iThus, there is no striking back of the iiame, due to the fact that thevelocity of the gases through the bushing f is greater than the velocityof flame propagation with the mixture at the temperature prevailingWithin the bushing. The combustion chamber, on the other hand, being ofrefractor material and suitably insulated, retains su ficient heat forthe preservation of the high temperature required for effecting the complete combustion as aforesaid. Nevertheless, it must not be possible fortlfie walls of the combustion chamber to accumulate so great a quantityof heat as to incur the risk of fusing the refractory material or itscasing.

It will be observed that the compression springs la serve for holdingthe fitting e' tight against the bushing f and for holding the bushingf, nipple fm., combustion chamber a, nozzle c and flange b in tightendwise engagement, but nevertheless'with such resilience as to permitof expansion and contraction l,and of vibration of the parts withoutrisk of fracture of the refractory material.

According to the modification 4illustrated in Figures 3, 4 and 5, themixing chamber is a 'jacketed tube comprising a cooling jacket 1enclosing the tubular mixing chamber 2. Near the rear end it is formedwith an ignition chamber 3 perforated at 4 to receive a sparking plug ora torch device, the ignition chamber being provided with port or ports 5leading to the mixing chamber 2. The chamber 3 may have also a screwthreaded hole 6 to receive a cock with air pipe connection, the cockbeing opened for a few seconds prior to ignition in order to blow out orscavenge any products of combustion remaining in the burner afterprevious use. The air and gas supply fitting 7, comprises two annularchambers 8 and 9 separated by the inner wall of both chambers, beingclosed at the rear end by a. glass window retained in position by a cap13. Several interehangeablenozzles 11 of different effective dimensionsmay be provided so that conditions can be suited by the removal of onenozzle and the insertion of another. The air and gas supply fitting isformed at its forward end with a spigot adapted to engage in an annulardepression or recess in the end of the mixing chamber. A concentric ring14 is interposed in the recess between the spigot and the end of themixing chamber and the internal diameter of thisring deter mines thesuperficial area of the annular passage through which the compressed airpasses to mingle with the gas issuing from the nozzle 11. Severalinterchangeable rings of different internal diameters may be providedwith a burner so that any one of these rings may be employed accordingto circumstances. The fitting 7 is secured in any convenient manner, forexample, by means of screws 16. The forward end ofthe wall enclosing thechamber 8 is coned or of nozzle form as is also the inner wall of theignition chamber 3. If desired, the mixing chamber may be provided witha nest of small tubes or gauze gratings, or with a Meaker grid 17 ofknown construction to prevent lighting back. The cooling jacket 1 may beprovided with water inlets and outlets 18 and 19, as shown in Figure 5.A nipple ring 21 with an expanding bore is inserted between the mixingchamber` 2 and the combustion chamber 20 and packing rings 22 and 23 ofasbestos or the like are suitably inserted between these parts. As inthe previous example, the forward end of the combustion chamber isfitted with a vena contracta nozzle and an asbestos ring 25 is insertedbetween it and the combustion chamber 20, a similar ring 2G beinginterposed between the nozzle 24 and the flange 27 of the metal casing28.

The rear end of this casing is somewhat enlarged as is also theY outerwall of the water jacket 1- and the latter is grooved to receive packingrings 29 which make a tight joint in the enlarged part of the metalcasing 28. It should be noted that there is a dead air space 30 betweenthe combustion chamber 20 and the casing 28 and also a smaller dead airspace or clearance between the outer wall of the water jacket 1 and thesaid casing. The rear end of the casing is provided with a fiange 31 andthe jacketed mixing chamber is formed with radial arms carrying eyes 32for passing on to studs 33 on the flange 31. 'Resilient bodies 34 arepassed on to the studs and compressed by the tightening of nuts 35. Theholes 36 in the flange 31 are adapted to receive bolts not shown forsecuring the burner in place to a bracket or other object.

The parts of the burner in Figures 3 to 5 are readily assembled, and theresilient bodies or springs hold them together with sufiicient pressurefor making good joints whilst avoiding any danger of breaking therefractory parts. The flame is ignited by a sparking plug or a torchinserted into the ignition chamber 3 before full pressure is turned on.As the pressure is increased, the

velocity in the ymixing tube 2 is increased, and the flame travels alongthe/tubular combustion chamber 20 and remains there owing to thevelocity'in the mixing tube 2 being lll l eater than the velocit offlame ropagachamber to be packed against a machined filon. The mixingtubey2 is cooledJ by the metal surface a liner tube 84 formed with'anjacket 1, particularly when water is circulated in this jacket and heataccumulates 1n the wall of the combustion chamber 20, with the sameresult as that above described in connection with Figure 1. v

According to the further modifications 1llustrated in Figure 6, which issomewhat similar to that described with referenceto Fi ures 3, 4 and 5,the cooling jacket 41 1s ex nded so as to enclose the refractory wall 43of the combustion chamber. -If desired, an acid-proof covering 44, suchas rubber` or l vulcanite, may be applied to the outer surface of theburner casing 45 when it is to be immersed in corrosife liquor. Theforward end of the covering 44'is turned in ins1de the end flange 46 ofthe casing and a. packing ring 47 is inserted between the covered flange46 and the vena contracta nozzle 48. A packing ring 49 is insertedbetween the nipple50 and the end of the mixing chamber 42, and packingrings 51 and 52 are inserted at respective ends of the wall 43 of thecombustion chamber. For use in corrosive liquids, the combustion chambermay be made entirely of silica or other appropriate material.

The extended portion of the. cooling jacket is merely for the purpose ofvpreventing fusing of t e walls or parts of the combustion chamber, andit must not rob the refractory wall 43.0f so much heat as to prevent itfrom having the high temperature necessary for the attainment ofcomplete combustion in the manner above explained.

In the modification in Figure 7 which also is somewhat similar to Figure3, the nozzle fitting is attached by the means 32 to 35 described withreference to Figures 3 to 5. According to this modification, however,the outer casing 71 is made of refractory Inatcrial and in one piecewith an inner tubular part 72 which is the wall of the combustionchamber. The walls 71 and 72 are spaced apart so as to provide ajacketspace 73 and a suitable formation is imparted at 74 to constitutethe burner nozzle. The inner end of the tubular art 72 is coned or taered at 73 to reduce the bore to that of the tu ular mixing chamber 76.As the casing 71 is of refractory material, the attachment flange 77must be made separately, and for holding the casing 71 a socket ring 79is passed over the casing and secured to the flange ring 77 by screws78. The socket ring is formed with an interned flange 80 for pressing arubber or other gasket 81 against an end flange 82 of the casing 71. Thejacket space 73 may be a dead air space, or it may be packed withgranular refractory material or other heat insulating material. Thetubular mixing chamber 76 is formed with a cooling jacket 83. In orderto enable the mixing inturned flange 85 at its inner end, is insertedinto the casing 71, the flan e 85 fitting loosely around `the reducedend o the tubular part72 and forming a partition between the jacketspace 73 and t-he space in which the coolingr jacket 83 is' situated.Packing rings 86 around the mixing. tube jacket make a. tight. jointwith the liner tube 84, and a packing ring 87 makes a. tight jointbetween the flange 77 and the end flange 82 of the casing. Also, apacking ring 88 makes a tight jointl between the. abutting ends of thetubular mixing and combustion. chambers. The operation of this burnerneeds no\de scription. The Inode of resiliently holding together andpacking the parts, enables -refractory material to be employed for thecasing without. liability to fracture. If desired, thetubular.combustion chamber 72 may be made separately froln the casingand may be inserted into the latter and jointed therewith at the lines89.

The construction in Figures 8 and 9 is similar in many respects to theconstruction in Figure 7. However, in Figure 8 itwill be seen that thecombustion chamber is composed of two tubular parts 91, 92 of refractorymaterial having the nozzle formation 93 and expanding nipple formation94 formed thereon. The said parts 91, 92 are made separately from thecasing 95 which is of refractory material and is attached to a socketring in the manner described with reference to Figure 7. Also, therefractor casing has a metal liner as' described wit reference to Figure7. The jacketed tubular mixing chamber comprises inner and outercylindrical walls 96 and 97 1respectively, and an intermediate wall 98which stops short at the inner end to leave a communicating passage 99between the two annular chambers enclosed by the walls, Thus, coolingair, being admitted at 100 to the outer jacket space, flows `inwardly tothe passage 99 and then performs a return flow to the outlet 101, thesaid air becoming heated or warmed in its passage. It may be veryadvantageous in some constructions to employ this warmed or heated airfor combustion purposes, and in this event thel air is conducted fromthe outlet 101 into an air supply chamber of an air and fuel sup lyfitting such as has been described. with re crence to preceding figures.Figure 9 illustrates a convenient construction of ignition chamber 102which extends through the double jacket just described, the port 104 ofsuch ignition chamber being disposed just in advance of the grid, gauzeor like device 103. This point of ignition is very convenient andadvantageous, and u on ignition taking place and the pressure of) thesupply being increased, the flame travels along the mixing tube and ismaintained in the combustion chamber 1n the manner hereinbeforedescribed.

Other modifications are possible without departing from the sco e of theinvention part of larger bore being adapted for high temperaturemaintenance during operation, and combustible iiuidmixture supply meansin communication with the part of smaller bore, the length of the partof larger bore being predetermined to ensure complete combustionwithinthe burner, and the relation between the bores of these partsbeing such las to ensure that the velocity of the mixture from thesupply to the combustion chamber shall exceed the velocity of flamepropagation substantially as set forth.

2. A submersible burner comprising a tubular combustion chamber havingheat retaining walls, a tubular mixing chamber of smaller bore than saidcombustion chamber, said mixing chamber freely communicating with saidcombustion chamber and having heat dissipating walls, combustiblemixture supply means on said mixing chamber, and avena contracta nozzleon the outlet end of said combustion chamber, substantially as setAforth.

3. A submersible burner comprising a tubular combustion chamber havingheat resistive walls, a tubular mixing chamber of smaller bore than saidcombustion chamber and freely communicating with the latter, said mixingchamber having heat conductive walls, a fuel nozzle fitting at the freeend of said mixing chamber, said nozzle fitting comprising admissionmeans for air to mix with the jet of fuel injected into said mixingchamber, and a contracting nozzle at the outlet end of said combustionchamber.

substantially as set forth.

4. A submersible burner comprising a tubular combustion chamber havingheat resistive walls, a tubular mixing chamber of smaller bore than saidcombustion chamber, said chambers being axially aligned and freelycommunicating with one another and said mixing chamber having heatconductive walls, a fuel nozzle fitting on the inlet end of said mixingchamber, and resilient connecting means for securing these partstogether in axial alignment substantially as set forth.

5. A submersible burner comprising a cylindrical casing, a refractorytube and a heat conductive tube of smaller bore than said refractorytube arranged end to end within said casing, a fuel nozzle on the freeend of said heat conductive tube, and resilient retaining meansoperative between said casing and one of said tubes substantially as setforth;

6. Al submersible burner comprising a cylindrical casing enclosing, inthe order named, a contracting bore tha-n said refractory tube, a fuelnozzle fitting on the free end of said heat conductive tube, andresilient retaining means j operative between said casing and the heatconductive tube, substantially as set forth.

7 A submersible burner comprising a cylindrical casing enclosing arefractory tube, having a contracting nozzle ring at each end and a heatconductive tube having a smaller bore than the refractory tube, the boreof intermediate nozzle ring expanding from the bore of the heatconductive tube to that of the refractory tube, a fuel injector deviceon the free end of said heat conductive tube, and resilient retainingmeans operative between said casing and the last named tube,substantially as set forth. Y

8. A submersible burner comprising a cylindrical casing enclosing, inthe order named, a contracting nozzle, a refractory tube and a heatconductive tube of smaller bore than said refractory tube,a fuel nozzlefitting on the free end of said conductive tube, said fitting comprisinga laterally disposed fuel admission, a peep device on the outer end ofsaid nozzle fitting and resilient retaining means operative between saidcasinor and the heat conductive tube, substantiaily as set forth.

9. A Submersible burner comprising a tubular combustion chamber havingheat retaining walls, a tubular mixing chamber of smaller bore and ofsubstantial length freely communicating With said combustion chamber, acooling jacket surrounding said mixing chamber, said jacket havingappropriate inlet and outlet for cooling fiuid, combustible mixturesupply means on said mixing chamber at the free end thereof and a nozzleat the outlet of said combustion chamber, substantially as set forth.

10. A submersible burner comprising a cylindrical casing, a burnernozzle, a refractory combustion tube and a heat conductive mixing tubeaxially aligned within said casing, means separating said refractorytube from said casing, cooling means on said mixing tube, a fuel nozzleon the free end of said mixing tube,vand resilient re- .taining meansoperative between said cas# lng and said mixing tube, substantially asset forth.

11. A submersible burner comprising a cylindrical casing, a burnernozzle, a refractory combustion tube and a heat conductive ozzle,agefractory tube and a heat conduc ivetube of smaller mixing tubeaxially ali ed within said Itive mixing tube of smaller bore than saidcombustion tube axially aligned within said casin a fuel nozzle fittingon the free end of sa1d mixing tube,l a flame guard between the bore ofsald mixing tube and said nozzle, and resilient retaining meansoperative between said mixin tube and said casing, substantially as setorth.

13. A submersible burner' comprising a cylindrical casing, a burnernozzle, a refractory combustion tube and a heat conductive mixing tubeof smaller bore than said combustion tube axially aligned within saidcasing, a fuel nozzle fittin on the free end of said mixing tube, saidtting comprising an ignition chamber and port in advance of said nozzleand a flame guard between such port and nozzle, and resilient retainingmeans operative between said mixing tube and said casing, substantiallyas set forth.

14. A Submersible burner comprising a cylindrical casing, a refractorycombustion tube of relatively large vbore and a metal mixing tube ofrelatively small bore axially aligned within said casing, jointin meansbetween said tubes and between sai refractory tube and the casing, anair and fuel supply fitting detachably secured to said mixing tube, andresilient retaining means operatlve between said mixing tube and saidcasing and adapted for compressing said jointin'g means, substantiallyas set forth.

15. A submersible burner comprising acylindrical casing havin anabutment. at one end a refractory nozz e ring ointedagainst saidabutment, a refracto combustion tube of relativel large bore tucentered. at one end in said7 nozzle ring, a reducing ni ple centered onthe other end of such com ustion tube, a mixing tube centered on saidnip le and having a bore corresponding wit '1 the reduced end of said nile, an air and fue] ,supply fitting detacha y secured to said mixingtube, and resilient retaining means operatlve axially between saidmixing tube and said casing, substantially as set forth.

16. A submersible burner comprising a cylindrical casing of refractorymaterial, metal mountin means affixed to the rear end of said casing, arefractory combustion tube in said casing and extending rearwardly fromthe forward end thereof, a metal mixing tube of smaller bore than saidcombustion tube, said mixing tube being inserted into said casingco-axially with and abutting against the rear end of said combustiontube, a fuel and air supply fittingl detachably secured to the rear endof said mixing tube, and resilient retaining means operative betweensaid mounting means and said mixing tube, substantially as set forth.

17. A submersible burner comprising a refractory tubular combustionchamber, a combustible mixture supply tube axially aligned and freelycommunicating at one end with the combustion chamber and having heatdissipating walls, the cross-sectional area of said tube being smallerthan the cross-sectional area ofthe combustion chamber, combustiblemixture supply-means on the free end of said tube adapted to impartvelocity to said mixture, a nozzle at the outlet,y of said combustionchamber, and resilient means securing the said tube and combustionchamber together.

' CECIL FEATHERSTONE HAMMOND.

